The invention relates to X-ray fluorescence analysis and more particularly to X-ray fluorescence analysis in an electron column instrument.
X-ray fluorescence analysis in electron column instruments has become increasingly popular with the advent of highly efficient solid state radiation detection devices. In such devices the electron beam in the column instrument impinges directly on the specimen, producing Bremsstrahlung X-rays and fluorescent X-rays characteristic of the atomic elements in the sample material. Analysis of the fluorescence X-rays gives information about the sample. Since the electron range in most materials is typically on the order of a few microns, the X-ray fluorescence is restricted to the elements on the surface of the sample. Furthermore, the Bremsstrahlung X-rays are an undesirable background radiation which is superimposed upon the fluorescence X-ray spectrum, thus masking low concentrations of trace elements in the sample. This is known as the direct electron excitation method. A second method known as the X-ray excitation method uses an X-ray beam which impinges on a specimen placed outside of the sealed-off X-ray tube. The X-rays thereby fluoresced from the specimen are analyzed.
One problem with such X-ray tube type analysis is that the X-ray tubes are self-contained, and intrinsically lack the versatility of the electron column instrument. Also, there is a certain amount of X-ray absorption between the X-ray source and the specimen. Still another problem of the X-ray tube device is that the X-ray cannot be as easily manipulated as the electron beam in the electron column instrument. Still another problem with the X-ray tube device is that the sample stages are not easily accessible and precisely manipulatable.